Conventionally, there are known devices that employ FPC's (Flexible Printed Circuits) in transparent tablets (touch panels) for inputting X-Y coordinates with fingers (refer to, for example, Japanese Unexamined Patent Publication No. 1(1989)-206425, FIG. 1). The FPC disclosed in the above document is continuously provided so as to surround the four sides at the periphery of a rectangular transparent substrate (transparent panel), which functions as an input portion of the transparent tablet. The FPC is formed in a frame shape by punching out a rectangular portion that corresponds to a display screen from a rectangular sheet FPC having greater dimensions than the display screen. The frame shaped portion is provided at the periphery of the transparent substrate, and electronic components necessary for the touch panel are provided on the frame shaped portion.
A circuit unit is also known, in which a single FPC is folded along two adjacent sides of a rectangular display screen of a plasma display device, a liquid crystal display device or the like (refer to, for example, Japanese Unexamined Patent Publication No. 2002-324951, FIG. 5).
In the case of the FPC disclosed in Japanese Unexamined Patent Publication No. 1-206425, it is easy to provide light emitting elements and light receiving elements such that their correspondent relationships are accurately established. However, the rectangular portion of the FPC which is punched out constitutes a large portion of the sheet FPC that it is punched out from. The punched out portion is generally discarded instead of being utilized. That is, the discarded portion becomes waste, the material utilization efficiency of FPC's, becomes low, and as a result, the cost of production becomes high. Even if the portion to be discarded is to be utilized for other applications, there are problems with regard to production and parts management. In addition, not all of the portions to be discarded can be utilized for other applications.
In the case of the FPC disclosed in Japanese Unexamined Patent Publication No. 2002-324951, the area of the FPC to be utilized can be maintained small. However, this configuration is difficult to be applied to a touch panel, in which an FPC is provided along the four sides of a rectangular transparent panel, and pluralities of light emitting elements and light receiving elements that correspond to each other are provided on the four sides.
The present invention has been developed in view of the foregoing circumstances. It is an object of the present invention to provide a touch panel, in which the material utilization efficiency of FPC's is high, which can be manufactured at low cost, and in which the correspondent relationships among pluralities of light emitting elements and light receiving elements can be accurately established.